Trachydolerite in Tasmania

In 1889 evidence was laid before this Society by Mr. W. F. Petterd and myself, demonstrating the existence in Tasmania of two centres or districts characterised by eruptive rocks derived from elaeolitic and theralitic magmas. I now submit further localities for rocks belonging to the same great felspathoid series. One of these is the Table Cape Bluff, near Wynyard, on the North-West Coast, and another is the Nut at Circular Head. A third is One Tree Point, Sandy Bay, near Hobart, where melilite, basalt has been identified, but only the first two will be dealt with in these notes

Discovery of an aboriginal chipped flake in deep ground near Gladstone

I happened to be at Gladstone last March when a worked stone of chalcedony was brought to me as a strange specimen found by Mr. Richards in working Richards's and Murray's alluvial tin claim at the old Doone mine, north of the Ringarooma River, and two miles from Gladstone. I recognised it as an aboriginal Flake, but, to make sure, I submitted it to Mr. R. M. Johnston, whose knowledge of these implements is unrivalled, and lie at once pronounced it to be of human workmanship. The following day I proceeded to the claim in order to examine the conditions of occurrence. The actual block of gravel from which the stone had been picked had disappeared in sluicing, but I stood on the actual site of the discovery, and Mr. Richards, who enjoys a high reputation for reliability and integrity, explained to me all the attendant circumstances

On the occurrence of Spherulitic Felsite on the West Coast of Tasmania

Examples of this rock from four different localities have come under our notice, namely, from Zeehan, the Castray River, Trial Harbour, and Strahan, and upon these occurrences we now offer a few observations. Includes photographic plate

On Hauyne-Trachyte and allied rocks in the districts of Port Cygnet and Oyster Cove

The igneous rock at Port Cygnet, in Southern Tasmania, has been known for a long time by the name of felspar-porphyry. As the porphyritic crystals of felspar are rather strikingly displayed in the rock, specimens have now and again, through collectors, found their way to different parts of the Colony. Microscopical study of some of these samples made us aware that the handsome porphyries were soda-trachytes, and we classed them as such in our last year's sketch of the igneous petrology of Tasmania. Since then we have found the felspathoid mineral haiiyne or nosean in them, which confirms our previous determination, and a recent excursion to the locality has enabled us to recognise quite a group of these rocks, as well as to fix their geological age. Includes illustrations of transverse sections

On the occurrence of Limurite in Tasmania

This peculiar and interesting rock occurs in considerable quantity at North-east Dundas, on the property held under mineral lease by the Colebrook Prospecting Association (Section 216, 93m). It apparently consists of a huge contact mass, which is of an irregular lenticular form, being bounded on its eastern side by a hard dark-coloured metamorphic slate, probably of silurian age, and on the western side wholly or partially by green serpentine, which is in places much decomposed. Includes photographic plate of Limurite and Axinit

Supplementary note on Limurite in Tasmania

In this paper the authors refer to their note on the same rock presented to the Society last year, since when they have further examined it microscopically, and have studied its occurrence on the spot. They acknowledge their indebtedness to Mr. R. Williams, the Manager of the Colebrook, for many useful and interesting specimens. The mine is between Rosebery and Ringville, on the saddle of a hill about 1500 ft. above sea-level, and is remarkable for the quantity of pyrrhotite occurring in the rock, associated with copper pyrites in relatively small quantities. The authors do not regard the occurrence as a lode, but rather as a rock mass, in the form of an irregular dyke or intrusion

On the topaz quartz porphyey or stanniferous elvan dykes of Mount Bischoff.

This rock was first described by S. N. Wintle in 1875 as eurite porphyry, which it had been termed by Professor G. H. F. Ulrich, who, however, did not publish his description until 1877. In 1875 also the late Chas. Gould wrote as follows : — " Mount Bischoff is a conical eminence rising to about 2,500ft. above the level of the sea. ... It consists of a small protrusion of a porphyritic rock having a felsitic base, with granules and crystals of quartz and felspar ; it weathers white, and is honeycombed or vesicular on the surface, most probably from the decomposition and removal of pyrites, which is freely disseminated throughout in places!." Includes photographic plate

On some Igneous rocks from the Heazlewood District

The Heazlewood District is situated directly south-west of the township of Waratah, in the county of Russell, and has of late years been made fairly accessible in consequence of its importance as an active centre of mining industry. The geology is in several respects unlike that of any other portion of the island, as far as known; though no systematic investigation of it has yet been undertaken. It lies south of the great coastal basaltic sheet, and north of a series of ancient metamorphic schists, with the interpolated gneisses and masses of crystalline limestone of the Pieman River area. Geologically, its characteristic features may be said to commence at a locality situate on the main Waratah-Corinna road, and known as the 10-Mile, and to continue thence to the immediate neighbourhood of the 18-Mile Camp. It extends in a northerly direction a small distance beyond Mt. Cleveland, and is crudely bounded on the south by the Parsons' Hood Mountain, with an irregular interruption by the stanniferous granites which form the main feature of the Meredith Range. The characteristic which renders the area of special interest to the geological student, and to the petrologist in particular, is the occurrence of a series of local rocks, which include fine grained granitites and syenites with masses of serpentine, the latter being closely associated with gabbros and ultra-basic rocks. These last commonly appear as comparatively large intrusive dykes. Includes plate of Harzburgite, Olivine Norite, Pyroxenite and Lherzolite

On the Felsites and associated rocks of Mount Read and vicinity

Associated with the schists of Mount Read and district are some obscure igneous rocks, siliceous in nature, compact in grain, often slightly schistose, which are what the field geologist calls felsites or felstones. These terms, however convenient, need explanation, for in different countries they carry different meanings. In Germany the word felsite (or micro-felsite) is applied to the compact homogeneous-looking groundmass of quartz porphyries

On the occurrence of Obsidian "Buttons" in Tasmania

The little grooved and rounded discs of lava known as obsidian buttons (and among local miners as fossil gum seeds [eucalyptus] or pods) found occasionally in the tin drift at Thomas Plains, Eastern Tasmania, and at Long Plain, near Waratah, have not attracted much attention hitherto, but are now acquiring particular interest from European researches in connection with similar occurrences elsewhere. They are by no means plentiful, and only eight specimens have come into our hands ; six from Thomas .Plains, one from Mr. Cherry's property at Springfield, near Scottsdale, and another from Long Plain. They are generally nearly hemispherical in shape, with a few concentric rings or flutings round the hemisphere. The edge of the disc is smoothly irregular, with distant sub-depressions. The flattened side or base is slightly concave, with a central convex elevation, which is ringed round with a distinct beading. In colour they are intense black, somewhat dull from a thin epidermal skin. The merest fracture, which is conchoidal, shows a lustrous glass beneath